The present invention relates to a Moineau pump or to an eccentric screw pump or eccentric screw compressor. Such Moineau pumps or eccentric screw pumps are known, for example, from U.S. Pat. No. 1,892,217. These pumps have an annular outer element and an inner element which is arranged in the inside of the outer element. The inner side of the outer element as well as the outer side of the inner element have a helical structure, wherein the structure of the outer element has one screw turn or winding or tooth more. The inner element moves in the inside of the outer element relative to this on an eccentric path, wherein the inner and/or the outer element may be moved for this.
A basic problem with Moineau pumps designed in a conical manner is the axial forces occurring in a pulsating manner. Here, great peak forces may occur, in particular with pumps for large delivery heads, which make it necessary to press the inner and outer element of the pump together with accordingly large axial forces. On the one hand the wear, but on the other hand also the starting moment for the drive of the pump, are increased on account of the increased friction.